The study looked at whether cities close to each other can benefit from being in a cluster, even if they are not all in one big city. They found that in the USA, cities in polycentric areas with multiple centers actually have higher productivity than cities in single-center areas. This means that being near other similar-sized cities can help a city grow and be more productive. Polycentric areas outperform single cities in terms of wages and productivity in many sectors. This shows that having cities close together can be good for the economy, even if they are not all in one big city.